In cardiac surgery, the patient's blood is heavily diluted with saline solution to reduce its viscosity and improve the manageability of the cardiopulmonary bypass circuit. The resulting extra volume of diluted blood is stored in a venous reservoir interposed between the vena cava tap and the pump of the heart-lung machine, which pumps the blood through an oxygenator and back into the patient's aorta. The venous reservoir also serves as a fluid buffer in the external circulation system to smooth out variations between the blood flow available from the vena cava and the demands of the heart-lung machine pump.
Because a substantial amount of blood escapes into the patient's chest cavity during the surgery, it is necessary to recover this cardiotomy blood with a suction device, filter it, defoam it, and then return it to the external circulation system. Although cardiotomy blood filtering and defoaming was originally done in a hardshell cardiotomy reservoir separate from the then collapsible venous reservoir, it has become conventional in recent years to combine the cardiotomy reservoir and the venous reservoir into a single hardshell venous reservoir.
A representative type of conventional hardshell venous reservoir has two distinct fluid paths: a venous blood path which enters the reservoir through a centrally located venous intake in the cover of the reservoir, and is conveyed into a defoaming chamber in which any air bubbles present in the venous blood are removed before the venous blood is discharged into the body of the reservoir.
The cardiotomy blood enters the reservoir through a plurality of cardiotomy inlet connectors in the cover of the reservoir (typically, three or four separate cardiotomy suction devices are used during cardiac surgery) and is conveyed into a much more elaborate filtering/defoaming chamber where cellular and surgical debris and large amounts of air are removed from the cardiotomy blood.
In use, the reservoir is typically so positioned as to be close to the patient, with the venous inlet connector turned toward the patient to minimize the length of the relatively large line from the vena cava. The suction pumps for the cardiotomy circuit may, however, be placed most anywhere with respect to the reservoir; usually away from the patient or off to one side.
In prior art reservoirs, the cardiotomy inlet connectors were fixed or were swivelable through only a limited arc with respect to the venous blood intake. In the latter case, the cardiotomy blood from the inlet connectors was passed through a swivelable common conduit before entering the filter/defoamer chamber. Failure of that common conduit during swiveling would shut down the entire cardiotomy circuit.
The limited mobility of prior art connectors posed a problem for the perfusionist: having to bring a plurality of lines around the cover manifold of the reservoir, particularly when moving equipment during surgery, not only resulted in a maze of criss-crossing lines (a number of other lines are also attached to the reservoir cover for monitoring and other purposes), but subjected the lines to kinking under the weight of the blood.